Midrash su Isaia 31:5

(Exodus 12:13) "And the blood shall be for you as a sign": for you as a sign, and not for Me as a sign; for you as a sign, and not for others as a sign. "on the houses": What is the intent of this? Is it not already written (Ibid. 7) "on the lintel of the houses where they shall eat it"? This tells me only of the houses in which they eat it. Whence do I derive (the same for) the houses in which they sleep? From (here) "the houses where you are" — in any event. "and I shall see the blood": R. Yishmael was wont to say: Isn't everything revealed to Him, viz. (Daniel 2:22) "He knows what is in the darkness, and light dwells with Him," and (Psalms 139:12) "Darkness, too, is not dark for You." What, then, is the intent of "And I shall see the blood"? In reward for the mitzvah that you do, I shall reveal Myself with compassion to you, as it is written (Ibid.) "ufasachti upon you," "pesichah" connoting life, as in (Isaiah 31:5) "As birds that fly, so will the L rd of hosts shield Jerusalem, shielding and saving, paseach and rescuing." Variantly: "And I shall see the blood": I shall see the "blood" of the binding of Isaac, as it is written (Genesis 22:14) "And Abraham called the name of the place 'The L rd will see.'" And elsewhere it is written (I Chronicles 21:15) "But as he was about to destroy, the L rd saw and He repented Himself of the evil." What did He see? The blood of the binding of Isaac.

"and you shall not go out, a man from the door of his house: We are hereby taught that once permission has been given to "the destroyer" to destroy, he does not distinguish between the righteous and the wicked. As it is written (Isaiah 26:20) "Go, My people, enter your chambers and close your door behind you. Hide but a little moment, until the wrath passes," and (Ezekiel 21:8) "Behold, I am (coming) upon you, and I will draw My sword from its sheath, and I will cut of from you (both) righteous and wicked." And it is written (Exodus 33:22) "And it shall be, when My glory passes by … and I shall cover you with My palm until I have passed." Variantly: (Exodus 12:22) "And you, do not go out, a man from the door of his house until morning" — to teach you that when you take to the road, enter (the house) in "ki tov" (i.e., in the morning) and leave in "ki tov" (from Genesis 1:4 "And G d saw the light ki tov" ("that it was good"). And thus do you find with the forefathers, that they deported themselves with circumspection (in this regard), viz.: (Genesis 22:3) "And Abraham arose early in the morning," (Ibid. 28:18) "And Jacob arose early in the morning," (Exodus 34:4) "And Moses arose early in the morning," (I Samuel 15:12) "And Samuel arose early in the morning to meet Saul." Now does this not follow a fortiori, viz.: If the fathers and the prophets, who were on the way to do the will of Him who spoke and brought the world into being, conducted themselves with such circumspection, how much more so (should) others (do so)! And thus is it written (of this natural order) ((Psalms 104:20-21) "You bring on darkness and it becomes night. In it stir all the beasts of the forest. The lions roar for prey, etc." (28) "You give it (food) to them and they gather it in, etc." — (22) "When the sun rises, they return" (to their lairs) — after which (23) "Man goes out to his work, to his labor, until the evening." (Exodus 12:23) "And the L rd will pass through to smite Egypt": as a king, who passes from place to place. "and he will see the blood": (see above on 12:13). "and the L rd will skip over the blood": Now does this not follow a fortiori, viz.: If of the blood (on the door) of the Pesach of Egypt, the less "formidable," which obtains only for a circumscribed time, and which did not obtain (both) in the daytime and at night, (but only at night), and which does not obtain for future generations, it is written (Ibid.) "and He will not permit the destroyer, etc.", then (the mitzvah of) mezuzah, the more formidable, containing (in Scripture) ten citations (of the name of the L rd), and which obtains (both) in the daytime and at night, and which obtains for all generations, how much more so should He not permit the destroyer, etc."! But why is this not the case? Our sins have prevented it. As it is written (Isaiah 59:2) "But your transgressions have separated between you and your G d, and your sins have hidden His face from you against hearing."